Fallback для localStorage в private mode мобильного сафари

storage.js

/**
 * Create instance of Cookie.
 *
 * @constructor
 * @this  {Cookie}
 */
function Cookie(name) {
  /** **/
}

/**
 * getter
 *
 * @this  {Cookie}
 * @return {string} value
 *
 * @static
 */
Cookie.prototype.getItem = function(name) {
  name = name.toString();
  var matches = document.cookie.match(new RegExp(
    "(?:^|; )" + name.replace(/([\.$?*|{}\(\)\[\]\\\/\+^])/g, '\\$1') + "=([^;]*)"
  ));
  return matches ? decodeURIComponent(matches[1]) : '';
};

/**
 * setter
 *
 * @this  {Cookie}
 *
 * @static
 */
Cookie.prototype.setItem = function(name, value, options) {
  options = options || {expires: '', path: '/'};
  name = name.toString();
  value = value.toString();

  var updatedCookie = name + "=" + encodeURIComponent(value) +
        ((options.expires) ? "; expires=" + options.expires : "") +
        ((options.path) ? "; path=" + options.path : "") +
        ((options.domain) ? "; domain=" + options.domain : "") +
        ((options.secure) ? "; secure" : "");

  if (byteLength(document.cookie) <= 4000) {
    document.cookie = updatedCookie;
  } else {
    alert(window['overQuotaMessage'] || 'Вы превысили максимальный размер cookies')
  }
};

/**
 * Create instance of Storage.
 *
 * @constructor
 * @this  {Storage}
 */
function Storage() {
  try {
    localStorage.setItem('foo', 'bar');
    localStorage.removeItem('foo');
    this.store = localStorage
  } catch (e) {
    this.store =  new Cookie();
  }
}

/**
 * getter
 *
 * @this  {Storage}
 * @return {string} value
 */
Storage.prototype.getItem = function(name) {
  return this.store.getItem(name);
};

/**
 * setter
 *
 * @this  {Storage}
 */
Storage.prototype.setItem = function(name, value) {
  return this.store.setItem(name, value);
};

/**
 * returns the byte length of an utf8 string
 *
 * @param  {string} str - utf8 string
 * @return {number} byte length
 */
function byteLength(str) {
  var s = str.length;
  for (var i=str.length-1; i>=0; i--) {
    var code = str.charCodeAt(i);
    if (code > 0x7f && code <= 0x7ff) s++;
    else if (code > 0x7ff && code <= 0xffff) s+=2;
    if (code >= 0xDC00 && code <= 0xDFFF) i--; //trail surrogate
  }
  return s;
}